Increased breakage of chromosome 1 in lymphocytes of patients with testicular cancer after bleomycin treatment in vitro

Long-Term Follow-Up Study of Genome Damage Elimination in Patients with Testicular Seminoma Exposed to Ionising Radiation during Radiotherapy

The rate of genome damage elimination after therapeutic exposure to ionising radiation was estimated in stage I testicular seminoma patients monitored over a seven-year follow-up. DNA damage elimination in peripheral lymphocytes of ten subjects was analysed by the chromosome aberration assay. Seven years after the end of radiotherapy, significantly increased frequency of ring and dicentric chromosomes was still detected in comparison with baseline values. These results indicate the induction of genome instability. Long-term follow-up studies of cancer patients after radiotherapy could give us valuable information on the rate of genome damage elimination after exposure to ionising radiation and about the duration and manifestation of genome instability. This may be used in health risk assessment related to the possible development of secondary neoplasia. Studies such as this could have a great value both for oncology and radiation protection management protocols, especially after accidental overexposures.

Schedule dependent variation in human lymphocyte sensitivity to bleomycin and repair of chromosomal aberrations in G2

Bleomycin (BLM) induced chromosomal damage in G2 phase and its repair kinetics in normal human lymphocytes were studied following different treatment schedules. As a first step, a dose-response curve was obtained (concentrations of 5-50 micrograms/ml). For repair kinetics studies, blood samples were treated with BLM at a concentration of 20 micrograms/ml. Continuous treatment produced equal numbers of breaks per cell (br/c) when the cells were treated 3, 4 or 5 h before fixation. If the treatment time was extended to 6 h, the level of br/c was increased 2-fold (p < 0.001) as a result of an increased number of cells with more than 3 br/c. The curves obtained after pulse treatment showed maximal chromosome damage at time 3 (45 min BLM treatment, followed by 2 h repair in drug free medium). When the time after treatment was extended to 4 h (treatment time 5), a 50% reduction in chromosome damage was measured. It was found out that at treatment points 3, 4 and 5 the differences in breaks per cell at the different schedules applied were statistically highly significant. If caffeine (CAF) was added, the continuous treatment, BLM+CAF, induced a statistically significant increase in the frequency of br/c at every treatment point, but the shape of the curve illustrating the kinetics of chromosomal damage remained unchanged. Moreover, the addition of CAF at continuous BLM treatment brings the level of br/c close to that measured at the pulse BLM treatment except for treatment time 3. When applied in a combination with BLM, CAF considerably modified the kinetics of chromosome damage for a pulse (BLM alone) treatment. The possible reasons for the changes in the level of br/c as well as a tentative scheme for assessment of chromosome damage repair capacity after BLM treatment are discussed.

No evidence for constitutional chromosome instability in testicular cancer

Chromosome aberrations in 20 lymphocytes of 20 patients with testicular germ cell tumors (TGCT) treated with surgery alone were compared with those of 20 cells from 20 healthy controls using standard G-banding technique. No increase in structural aberrations was found in the cancer group. An unexpected finding was that of more cells with losses of chromosomes being present in the control group. These losses predominantly affected small chromosomes in the control group, whereas the pattern of chromosome loss was different in the cancer group. The literature claiming increased chromosome instability in TGCT patients is reviewed. Point estimates and 95% confidence intervals to exclude such a hypothesis based on our results were calculated.

Bleomycin-induced chromosomal damage in tuberous sclerosis

To investigate the possible involvement of mutagen-induced chromosomal instability in tuberous sclerosis the blood lymphocytes obtained from eleven patients with this disease and eleven healthy controls of comparable age and sex were exposed to bleomycin in vitro during the late S and G2 phases of the cell cycle. Neither the spontaneous aberration yields nor the bleomycin-induced chromosomal sensitivity differed between the two groups. The chromosomal distribution of 578 and 478 induced breaks in patients and controls, respectively, was similar. Thus, bleomycin-induced G2 chromosomal hypersensitivity in lymphocytes of patients with tuberous sclerosis is not an intrinsic feature of this hereditary disease.

Carcinoma in situ in testicular biopsies

Carcinoma in situ of the testis is an abnormality of the seminiferous epithelium characterized by aneuploid cells with clear cytoplasm located along the tubular basement membrane or in the lumina of tubules. Morphological, cytogenetic, and histochemical features of this anomaly are presented. An adequate fixation of testicular tissue samples is necessary for correct diagnosis. The fact that approximately 50% of carcinoma in situ may develop into malignant germ cell tumours of the testis in 5 years and the investigations of the testicular tissue adjacent to these tumours support the malignant nature and invasive potential of testicular carcinoma in situ. The incidence of carcinoma in situ in persons at risk is reviewed.

Increased bleomycin-induced chromosome damage in lymphocytes of patients with common variable immunodeficiency indicates an involvement of chromosomal instability in their cancer predisposition

To study mutagen-induced chromosome instability in cancer disposition, late S and G2 lymphocytes of 15 patients with common variable immunodeficiency and 14 healthy controls were exposed to bleomycin in vitro. The groups did not differ in the frequency of spontaneous chromosome aberrations. In bleomycin-treated samples we found higher numbers of break events per cell and increased frequency of cells with aberrations compared to the control group. A slightly reduced breakage of chromosome group D was noted in patients. These results support the hypothesis that a higher incidence of cancer in patients with genetically determined immunodeficiencies may be explained by an increased mutagen-induced chromosome instability in at least some of them.